Epoxy thermoset resins are one of the most widely used engineering resins, and are well-known for their use in adhesives, coatings and composites. Epoxy resins form a glassy network, exhibit excellent resistance to corrosion and solvents, good adhesion, reasonably high glass transition temperatures, and adequate electrical properties.
A thermosettable or curable epoxy resin formulation typically uses a curing agent, such as an amine curing agent, for crosslinking the epoxy resin to form a cured product such as a composite or laminate. The reactivity of epoxy resin formulations used in composite applications is commonly adjusted by the addition of accelerators. Known standard accelerators for epoxy/amine systems include, for example, bisphenol-A, nonylphenol (NP), the combination of NP and aminoethylpiperazine (AEP), and benzyl-alcohol.
Each of these known accelerators suffers from one or more problems when used in epoxy resin formulations for preparing a cured composite article. For example, while bisphenol-A has the advantage of being very efficient and relatively inexpensive, bisphenol-A has the disadvantage of crystallizing easily in formulated systems, and hence, the use of bisphenol-A creates handling and processing issues. NP presents the disadvantage of having a very negative toxicological profile; the combination of NP and AEP produces an extremely fast and highly exothermic reaction with epoxy compounds; and benzyl-alcohol is volatile, and also significantly decreases the cured properties of an epoxy resin, such as glass transition temperature which is a critical property for many applications.
It is therefore desired to provide a readily available, affordable, accelerator component for epoxy resin formulations; wherein the accelerator has a similar or improved acceleration effect as compared to prior art accelerator systems without the problems of the prior art accelerators and without compromising the overall physical properties of the original epoxy resin formulation containing a curing agent, wherein the epoxy resin formulation is used in producing composites.